全文获取类型
收费全文 | 440008篇 |
免费 | 36122篇 |
国内免费 | 15959篇 |
专业分类
耳鼻咽喉 | 2881篇 |
儿科学 | 7673篇 |
妇产科学 | 5006篇 |
基础医学 | 68780篇 |
口腔科学 | 8011篇 |
临床医学 | 31937篇 |
内科学 | 75451篇 |
皮肤病学 | 6472篇 |
神经病学 | 30566篇 |
特种医学 | 10061篇 |
外国民族医学 | 106篇 |
外科学 | 41620篇 |
综合类 | 60262篇 |
现状与发展 | 55篇 |
一般理论 | 6篇 |
预防医学 | 23479篇 |
眼科学 | 5217篇 |
药学 | 58634篇 |
106篇 | |
中国医学 | 17021篇 |
肿瘤学 | 38745篇 |
出版年
2024年 | 1074篇 |
2023年 | 6811篇 |
2022年 | 14521篇 |
2021年 | 18471篇 |
2020年 | 14841篇 |
2019年 | 16433篇 |
2018年 | 15520篇 |
2017年 | 14948篇 |
2016年 | 14698篇 |
2015年 | 17285篇 |
2014年 | 26539篇 |
2013年 | 29009篇 |
2012年 | 26042篇 |
2011年 | 30035篇 |
2010年 | 25383篇 |
2009年 | 25417篇 |
2008年 | 23601篇 |
2007年 | 22829篇 |
2006年 | 20474篇 |
2005年 | 17496篇 |
2004年 | 14299篇 |
2003年 | 12498篇 |
2002年 | 9899篇 |
2001年 | 8502篇 |
2000年 | 7062篇 |
1999年 | 6326篇 |
1998年 | 5492篇 |
1997年 | 5145篇 |
1996年 | 4454篇 |
1995年 | 3963篇 |
1994年 | 3507篇 |
1993年 | 2886篇 |
1992年 | 2500篇 |
1991年 | 2208篇 |
1990年 | 1823篇 |
1989年 | 1521篇 |
1988年 | 1401篇 |
1987年 | 1153篇 |
1986年 | 1124篇 |
1985年 | 2185篇 |
1984年 | 2314篇 |
1983年 | 1638篇 |
1982年 | 1685篇 |
1981年 | 1390篇 |
1980年 | 1221篇 |
1979年 | 1006篇 |
1978年 | 757篇 |
1977年 | 607篇 |
1976年 | 626篇 |
1975年 | 511篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Mohammad Aftabuddin Ichiro Yamadori Tadashi Yoshino Eisaku Kondo Tadaatsu Akagi 《Pathology international》1995,45(6):422-429
The relationship between the number of apoptotic cells and the expression of apoptosis-related antigens was examined In 56 cases of non-Hodgkin's lymphomas and in 10 cases of reactive hyperplastic lymph nodes (RHL). Apoptosis was visually quantified by the in situ end-labeling (ISEL) method, and the expression of Fas, Ley antigens and bcl-2 protein was examined by Immunohistochemistry. The expression of Ley antigen was observed in germinal centers of RHL and 45% of non-Hodgkin's lymphomas. The apoptotic cell count (AC) in follicular lymphomas was significantly less than that in diffuse lymphomas. The distribution pattern of apoptotic cells In follicular lymphomas was inverse to that in RHL. In follicular lymphomas, AC was lower in follicles than in inter-follicular areas. In contrast, AC was higher in follicles than in Interfollicular areas in RHL. Ley antigen-positive lymphomas showed a significantly higher AC than the negative cases. The Fas antigen-positive lymphomas showed a higher AC than the negative cases. However, AC in bcl-2 protein-positive and negative cases was not significantly different. These results suggest that Ley and Fas antigens appear to be involved in the apoptotic tendency of tumor cells in non-Hodgkin's lymphomas, whereas bcl-2 does not necessarily. 相似文献
992.
L. Hübner E.M. Kniep H. Laukel C. Sorg H. Fischer W.D. Gassel K. Havemann B. Kickhöfen M.-L. Lohmann-Matthes A. Schimpl E. Wecker 《Immunobiology》1980,157(2):169-178
Supernatants from Concanavalin A-stimulated murine spleen cells were subjected to hydrophobic interaction chromatography on phenyl-Sepharose. Macrophage cytotoxicity factor (MCF), macrophage migration inhibitory factor (MIF), T-helper cell-replacing factor (TRF) and colony-stimulating factor (CSF) were bound at high ionic strength and were released stepwise at low ionic strength. CSF thus could be separated from MCF, MIF and TRF and the bulk of other proteins. Chromatography of pools containing MCF, MIF and TRF on Sephadex did not lead to a separation of the three activities which were all found in a molecular weight range of 25.000-55.000. Isoelectric focusing of these pools in pH range from 4 to 9 gave two peaks for MCF at pH 8.2 and 7.2, whereas MIF activity focused from pH 4.5 to 5.5. TRF activity was found in a single sharp peak at pH 5.3. The results demonstrate that the four biological activities can be distinguished on a chemical basis and are accessible for purification and chemical characterization. 相似文献
993.
Inge Van de Walle Karen Silence Kevin Budding Liesbeth Van de Ven Kim Dijkxhoorn Elisabeth de Zeeuw Cafer Yildiz Sofie Gabriels Jean-Michel Percier Johanna Wildemann Jan Meeldijk Peter J. Simons Louis Boon Linda Cox Rob Holgate Rolf Urbanus Henny G. Otten Jeanette H.W. Leusen Peter Boross 《The Journal of allergy and clinical immunology》2021,147(4):1420-1429.e7
994.
Objective: To investigate whether cockroach allergen extract can stimulate Protease-activated receptor 2 (PAR-2) expressed in mouse lung fibroblast.Materials: We established an immortalized lung fibroblast cell line, DM5, from PAR-2 deficient mice. By stable transfection with either an empty vector (DM5/EV) or an expression vector encoding mouse PAR-2 cDNA (DM5/Par2), a pair of lung fibroblast cell lines with or without functional PAR-2 expression were prepared.Treatment: The cells were exposed to cockroach allergen extract {up to 800 protein nitrogen unit (PNU)/ml}, trypsin (up to 100 nM), SLIGRL agonist peptide (up to 500 M), and trans-cinnamoyl-LIGRO agonist peptide (up to 400 M).Methods: The cells were loaded with Fluo-3 calcium indicator and mobilization of intracellular calcium with the stimuli was monitored by a fluorometric plate reader. Extracellular signal-regulated kinase (ERK) phosphorylation was examined by Western blot analysis using an anti-phospho ERK antibody.Results: The cockroach extract induced intracellular calcium transients in a concentration dependent manner in DM5/Par2 but not in DM5/EV. The activity was abolished when the cockroach extract was heat denatured or pre-incubated with PMSF (phenylmethanesulfonyl fluoride) prior to the assay. Concomitantly, ERK phosphorylation was seen in DM5/Par2 with the cockroach extract but not with a heat-denatured extract. The responses were sensitive to an inositol-1,4,5 triphosphate antagonist (2-APB) indicating that calcium was mobilized from intracellular store.Conclusions: Cockroach allergen extract can activate PAR-2 and thereby stimulate mouse lung fibroblasts likely through protease(s). The present study proposes a potential mechanism for cockroach antigens, similar to house dust mite antigens, in the etiology of respiratory diseases.Received 29 February 2004; returned for revision 12 April 2004; accepted by M. Katori 22 April 2004 相似文献
995.
996.
Nadine Gerin-Portier Jean Bourgeois Lucien Brasseur 《Pflügers Archiv : European journal of physiology》1970,314(4):263-273
Summary The differences inP
O
2readings between gas and blood were studied with a Clark-type electrode in the range of 38.5 to 713 mm HgP
O
2.The tonometered blood samples were taken in two different ways. The results showed that the gas-blood ratior
b(equilibrating gasP
O
2reading/equilibrated bloodP
O
2reading) depended not only on the sampling method but also on theP
O
2range: it varied from 1.005 to 1.032 for aP
O
2of 96.5 mm Hg, and from 1.040 to 1.081 for aP
O
2of 713 mm Hg according to the sampling procedure.A theoretical analysis demonstrated that the variation ofr
bwith the bloodP
O
2can be attributed to the influence of the degree of oxygen saturation of the hemoglobin on theP
O
2gradient existing in the blood diffusion boundary layer adhering to the electrode membrane.This work was supported by grants from the High Authority of the European Coal and Steel Community and from the Fonds de la Recherche Scientifique Médicale, Belgium. 相似文献
997.
Minute pieces of rat parotid gland were used in studies of adrenergic regulation of K+ efflux using 86Rb+ as a probe for K+. Noradrenaline induced a concentration-dependent Rb+ efflux, whereas the β1-selective agonist prenalterol was without effect. On the other hand, the β2-selective drug, terbutaline, at high concentrations displayed a small enhancement of Rb+ -secretion. The selective α1-adrenoceptor drug, phenylephrine, was as potent as noradrenaline, whereas the α2-agonist clonidine had only a small effect. The noradrenaline-induced Rb+-efflux was effectively inhibited in the presence of prazosin, an α1-blocker, whereas the α2-antagonist, yohimbine, was roughly 50 times less potent. The results suggest that catecholamine-induced K+-secretion from the rat parotid gland is mediated via activation of post-synaptic α-adrenoceptors of the α1-subtype. 相似文献
998.
David R. Harder 《Pflügers Archiv : European journal of physiology》1982,394(2):182-185
Some membrane electrical properties of muscle cells from the middle cerebral artery of the rat were recorded with intracellular microelectrodes. The resting membrane potential (E
m) of this preparation was –63 mV. Reduction of extracellular pH to 7.0 in the face of a constantP
CO
2of 40 mm Hg had no significant effect onE
m. Similarly the slope of the steady-state voltage/current curves was not different at pH 7.0 compared to control at pH 7.4. In marked contrast, whenP
CO
2was elevated to around 60 to 70 mm Hg there was a rapid hyperpolarization and reduction in the slope of the voltage current curve suggesting an increased conductance for one or more ionic species. In addition elevation ofP
CO
2increased the slope of theE
m vs. log[K]0 curve from 46 mV/decade to 59 m V/decade which is in good agreement with a Nernstian potential for a K+ selective membrane. These data suggest that while the smooth muscle cells of rat cerebral arteries are relatively insensitive to a small reduction in extracellular pH; reduction of intracellular pH by elevatingP
CO
2induces hyperpolarization by increasing K+ conductance (g
k). However, it is not clear from these experiments if theP
CO
2effects are mediated entirely by changes in pH or if there is a direct membrane action of CO2.This work is supported by Grant no. HL27862 相似文献
999.
1000.
Takaaki Ito Hitoshi Kitamura Yoshiaki Inayama Masayoshi Kanisawa 《Pathology international》1988,38(9):1097-1104
Chronic effects of 4-nitroquinoline 1-oxide (4 NQO) on the lungs of Syrian golden hamsters were studied. 4 NQO was subcutaneously injected weekly for 3 weeks at a dose of 20 mg/kg body weight. The animals were sacrificed at the 65th and 80th experimental weeks. Two cases of pulmonary adenomas were demonstrated in the 10 4 NQO-treated animals at the 80th week, and the tumor cells contained cytoplasmic lamellar inclusion bodies. In a previous study, we reported 4 NQO- induced pulmonary endocrine cell hyperplasias in the 4 NQO-treated hamster after the 20th experimental week (Jpn. J. Cancer Res., 77,1986). In the present study, 12 pulmonary endocrine cell hyperplasias were recognized in serial sections of the 24 treated animals. The hyperplastic lesions showed positive immunoreactivity to calcitonin. The hyperplastic lesion did not develop to pulmonary endocrine cell neoplasm. ACTA PATHOL JPN 38 : 1097∼1104, 1988. 相似文献